1. Field of the Invention
The present invention relates to the field of liquid crystal display, and in particular to a direct type LED backlight and a liquid crystal display thereof.
2. The Related Arts
With the continuous improvement of technology, the backlight technology of liquid crystal display is improved continuously. A traditional backlight of the liquid crystal display uses a cold cathode fluorescent lamp (CCFL). But CCFL backlight has some disadvantages of worse color reproduction, poor luminous efficiency, high discharge voltage, bad discharge feature at low temperature and taking long time to heat to achieve stable grayscale. At present, it has been developed using LED backlight technology.
LED backlight is mainly divided into direct type and edge type.
The direct type LED backlight denotes that LED is arranged at the back of the liquid crystal panel as backlight. The edge type LED backlight denotes that LED is arranged around the edge of the liquid crystal panel, in which the LED emits light through the light guide plate and to the entire display panel from the edge of the screen.
In the direct type LED backlight, multiple LED strings are arranged at the back of the liquid crystal panel, wherein, each LED string comprises multiple LEDs connected in series. In order to drive each LED string, it needs a specific drive circuit to offer drive voltage to each LED string.
FIG. 1 is a schematic view illustrating a direct type LED backlight according to the known technology. As shown in FIG. 1, the driving circuit of the backlight comprises a power converting circuit 110, a boost circuit 120, and multiple LED strings 130.
The power converting circuit 110 is used to convert an AC voltage (such as 110 V or 220 V) into a DC voltage (such as 5 V, 12 V, or 24 V). Generally, there is only one power converting circuit 110 used for AC-DC conversion in a liquid crystal display, which is used as a DC power source for the various electrical components in the liquid crystal display.
The boost circuit 120 is used to boost the DC voltage output from the power converting circuit 110, to satisfy the need of driving each LED string 130. In the present technology, the needed voltage for each LED string 130 is higher than the DC voltage output from the power converting circuit 110, which needs the specific boost circuit 120 to boost. Because of the presence of the boost circuit 120, the circuits of the entire liquid crystal display become complicate, and the costs increase.
Therefore, a direct type LED backlight with simple and low-cost circuit structure is needed.